An apparatus for ophthalmological treatment for which it is necessary to assure control is described for instance in the European patent document EP-B-0 030 210. The apparatus includes essentially a first light source which emits a laser power beam intended for treatment, and a second light source which emits a visible coherent light beam of low power arranged to envelop the power beam. Such beams then pass through a converging lens which concentrates them at a focal point, this being the point of treatment, the visible light beam being present in order to permit localization with precision of the place where the point of focus of the power beam is to be found. The point of focus is observed by a medical practitioner through an eye piece (or binocular) while the ocular cavity is illuminated by an auxiliary source of light. When the place sought for treatment is reached, the practitioner may fire the power beam.
Apparatus of the prior art may appear more or less as shown on FIG. 1. The treatment apparatus includes a table 1 in front of which a practitioner 2 may be seated. On the other side of the table will be found a patient 3, here recumbent on a bed 4 which is precision recessed into the table. In certain cases the patient is seated and rests his head on a chin rest fastened to the table. Whatever be the position chosen for the patient, the apparatus is conceived in order that the head of the patient be immobilized relative to the said apparatus.
FIG. 1 further shows a cabinet 5 supporting the table. This support generally contains sources giving rise to the power beam and the visible light beam as mentioned hereinbefore. These beams are led to the interior of the eye of the patient by a column 6 and a movable arm 7, this latter bearing an output optical system 8 adapted to focus the beams down to a point which must be brought to a precisely determined place within the eye of the patient, such point being observed by the practitioner through the binocular 9. To this end arm 7 may be displaced according to three orthogonal coordinate axes X, Y and Z.
In order to displace the beams coming out of the optical system 8 and to direct them to a precise point within the ocular cavity, the practitioner employs a contact lens 10 which is held on the eye of the patient. In this case his left hand 11 is occupied. The right hand 12 of the practitioner must thus be capable of alone operating the control arrangement 13 which is not described in the document cited hereinabove and which must permit control of at least four functions: that of displacement of the column 7 according to three coordinates X, Y and Z and that of firing the laser at the moment when the three coordinates which have been sought are attained. It can be readily imagined without any particular inventive activity that the control arrangement 13 includes four distinct elements controlling respectively the displacements X, Y and Z of the laser beam, the first three elements being rollers which may be operated in both senses and the fourth element being a simple push-button. Such an arrangement is awkward since it obliges the practitioner to memorize the location of the rollers and the functions which are attached to them with risks of error or loss of time that such a system may cause, since the eyesight of the practitioner is entirely occupied in observing the eye cavity to be cared for and must not be distracted to check for instance if the correct control element has been operated.